Best way to update some fields of a detached object on Hibernate?

Question

I was wondering what\'s the best way to update some fields of a dettached object using HB on Java. Specially when the object has child objects attributes. For Example (annot

Answer 1

After loading a Parent object, you said

Now, I only want to allow the user to update the field2 attribute of the parent

Based on Use case, you can use a UpdateableParent object

public class UpdateableParent {

   private String field2;

   // getter's and setter's

}

Now our Parent repository

@Repository
public class ParentRepositoryImpl implements ParentRepository {

    @Autowired
    private SessionFactory sessionFactory;


    public void updateSpecificUseCase(UpdateableParent updateableParentObject) {

        Parent parent = sessionFactory.getCurrentSession().load(Parent.class, updateableParentObject.getId());

        try {
            // jakarta commons takes care of copying Updateable Parent object to Parent object

            BeanUtils.copyProperties(parent, updateableParentObject);
        } catch (Exception e) {
            throw new IllegalStateException("Error occured when updating a Parent object", e);
        }

    }

}

Its advantages

• It is safe: you just update what you really want
• You do not have to worry about MVC framework (Some MVC framework allows you set up a allowedFields property). What happens if you forget some allowed fields ???

Although it is not a Technology-related question, Seam framework allows you update only what you want. So you do not have to worry about what pattern to use.

regards,

Answer 2

A) Retrive the Parent instance from the Session again and replace by hand the updated fields

this seems to be the most functional version which i used over the past few years.

B) Store the Child somewhere (httpSession?) and associate it latter.

I would advise against this, especially if you want to follow the REST paradigm which makes server side state a complete no-no. And you will end up using heap space for detached objects, although the user who initiated the session left for coffee :)

C) Set the relation between Parent and Child as immutable.

IMHO this is not a good way either, although it would be fit for a small project with an small persistence model. But even in a small application it might lead to a headache when trying to modify the code.

Answer 3

You can modify the detached object directly and then reattach the object to the session using the merge method on the session.